Earlier tests revealed that the Obama Vegetable Garden contained lead levels of 93 parts per million (p.p.m.). According to the U.S. Environmental Protection Agency, lead-concentration in soil is not hazardous until it reaches 400 p.p.m. Nevertheless, President Obama had work done to the garden to further reduce lead-concentration levels.
The soil was amended with lime, green sand, crab meal and compost made by the National Park Service. The pH was also adjusted between 6.5 and 7 because lead is unavailable to plants when the pH level is in that range. The lead-concentration level is now 14 p.p.m, which means the soil is now comparable to soil in places where there are no automobiles!